254) Theory of Lucas's Experiments. 



a flocky dark brown precipitate of humic acid, which, being carefully collected 

 and dried, weighed 0"27 grains. The liquid from c was of a darker colour, 

 and, with muriatic acid, yielded 0*43 grains of humic acid. 



Two drachms of each of the three portions of charcoal were reduced to 

 ashes in the platina crucible. The ashes of a weighed 22 grains, and lost, by 

 shaking with distilled water, one grain in weight. The ashes of h yielded only 

 9 grains of ashes, of which only half a grain was dissolved by the water. The 

 ashes of c, on the contrary, weighed 33 grains ; apparently because the char- 

 coal powder, while in use for two years, had become fouled with garden mould ; 

 of these 33 grains of ashes, two grains were dissolved in water. The consti- 

 tuent parts of the three portions of ashes retained their qualities ; so that in 

 the dissolvable parts were found potash, chalk, carbonic acid, sulphuric acid, 

 muriatic acid, and phosphate. The portion indissoluble in water contained 

 chalk, magnesia, traces of oxide of iron, carbonate, sulphuric acid, phosphate 

 and silicic acid. 



If the objection be made, with respect to these three portions of charcoal, 

 that they are not all from the same tree, and might therefore yield a different 

 weight of ashes, we may, with probability, suppose that this natural difference 

 is very inconsiderable, as the charcoal was all of fir wood from the neighbour- 

 hood of Munich, where limestone debris is the general understratum of the 

 woods. 



The result is quite decisive and undisputed, that diluted lie of potash 

 scarcely ever dissolves any thing from fresh fir charcoal, and that, on the con- 

 trary, charcoal in which plants have grown, being partly changed into humus 

 and this being drawn out by diluted lie of potash, amounted in the charcoal 

 b, after six months' use, to 2'23, and in the charcoal c, after being two years 

 in use, to 3'73 of 1000. By this it is also proved, that charcoal, under the 

 influence of light, air, water, and vegetation, is gradually decomposed, by 

 losing carbon ; in the place of which hydrogen and oxygen predominate, and 

 concur with the remains of carbonate to form humic acid. 



No less interesting is the further comparison of the ashes of, I may say, the 

 virgin charcoal a and the charcoal b, which had been used half a year for 

 vegetation ; in this instance a and b were in the proportion of 122 to 15 of 

 ashes from 1000 of charcoal. Undoubtedly the dissoluble salts were, in pro- 

 portion to the increasing decomposition of the charcoal, absorbed by the 

 roots. That the greater weight of the ashes of c is not decisive has been 

 already mentioned. To make very correct experiments of this sort, charcoal 

 from the same tree should be burnt, equally reduced to powder, and, in plant- 

 ing in this powder, all impurities of garden mould, &c., carefully avoided, and 

 watering the plants with rain-water attended to. 



5. Antiseptic Power of Charcoal. In judging of the effects of charcoal on 

 vegetation, its antiseptic properties are of great importance, for it has very 

 little power of retaining water, and the little it retains is partly absorbed by 

 the roots and partly evaporated. This property deserves the greatest atten- 

 tion of gardeners, in respect to recovering the health of plants the roots 

 of which have become injured by being in a clayey soil, and too freely watered, 

 or after continued rain, or being in contact with manure not sufficiently de- 

 composed. They should be immediately transplanted into charcoal powder, 

 as the most effectual method of cure. 



6. Liiterature. In all scientific examinations, if they have any pretension 

 to be well-founded, the greatest assistance may be procured from historical 

 and literary researches. In this instance, however, it is very remarkable that 

 all research in books which were at command was only a loss of time and 

 trouble. In Dietrich's Perfect Lexicon of Gardening and Botany, with the 

 Supplements, I looked in vain for the article " Charcoal," or " Charcoal 

 Dust." I did not find more in Piever's Encyclopedian Dictionary or in 

 Brockhaus's Conversations Lexicon. Leopold's Economical Dictionary contains 

 only the following short passage : '' Charcoal dust makes the earth light, and, 

 when when mixed with sand, is very useful in a clayey soil." 



